A network architecture comprising at least one core network, each core network comprising a number of packet data gateway access supporting nodes GASNs handling mobile user station access over an access network, said core network(s) further providing access to one or more global packet data communication networks (IN), and one or more nodes holding subscriber or mobile user station related information. The GASNs are further adapted to support intercommunication over a mobility protocol interface to, at reception of a request for change of access type from a mobile user station, establish information about the previous GASN of the mobile user station, and to, using the established information, update an established communication context concerning the mobile user station or create a new communication context concerning the mobile user station such that mobility between different access network types is enabled for a mobile user station without interruption of an ongoing session.